Monte Carlo simulation of the Compton scattering technique applied to characterize diagnostic x‐ray spectra

Abstract

The quality control of x-ray tubes for medical radiodiagnostic services is very important for such devices. Therefore, the development of new procedures to characterize the x-ray primary beam is highly interesting in order to obtain an accurate assessment of the actual photon spectrum. The Compton scattering technique is very useful to determine x-ray spectra (in the 10-150 kVp range), avoiding a pile-up effect in the detector since a large room is not usually available to apply other techniques. In this work, this process has been simulated using a Monte Carlo code, MCNP 4C. Some geometrical models have been developed and different techniques have been studied in order to improve statistics and accuracy in the acquisition of Pulse Height Distribution (PHD). The effect of both the collimation of the primary beam and the scattering angle of the spectrometer has been analyzed. Results obtained using simulation models have been compared with experimental measurements.

Estimating the absolute flux distribution for a synchrotron X-ray beam using ionization-chamber measurements with various filters

“…Fewell & Shuping (1977) have been pioneers in the use of spectrometer systems based on high-purity (intrinsic) Ge for such purposes. Compton scattering has been used as a means of circumventing the issue of excessive flux in the primary X-ray beam [see, for example, Gallardo et al (2004)], as has the Si surface barrier detector (Pani et al, 1987). 2 A number of other detectors have also been used including those based on: NaI (Tl) scintillation (Epp & Weiss, 1966); Xe proportional counter (Israel et al, 1971 3 ); Si (Li) (Cho et al, 1978); Ge (Li) (Birch & Marshall, 1979); Si PIN diodes (Aoki & Koyama, 1989); CdTe and CdZnTe (Takahashi & Watanabe, 2001).…”

Parametric study of the X-ray primary spectra obtained with the MTSVD unfolding method

“…Therefore, statistics of the simulation is very poor. To improve statistics the geometry is splitted in two parts, as was presented in Gallardo et al, (2004). The final result, obtained with an F8…”

“…To avoid the pile-up effect in the detector produced by a high fluence rate, a Compton spectrometry technique is proposed. In previous works (Gallardo et al, 2004) (Gallardo et al, 2006) The relation between the PHD and primary spectrum is defined by a Response function, expressed as a matrix. This Response matrix is ill conditioned and an unfolding method -such as MTSVD-should be applied to obtain the inverse matrix and hence the primary spectrum.…”

Measurement and Calculation of Compton Spectrometer Response Function for 10–60-keV Monoenergetic Photons

“…Xray spectroscopy in clinical situations is increasingly important for improving the image quality and reducing the patient dose. [1][2][3] However, direct measurement of the X-ray spectrum under clinical operating conditions is difficult, because of the extremely high fluence rate of the incident photons. Additionally, reducing the number of photons detected per unit time by increasing the distance between the source and detector is almost impossible for some radiographic devices, such as mammographic X-ray and computed tomography units.…”